The present invention relates to a color image forming apparatus, and more particularly to an image processing apparatus for performing proper color reproduction in a digital color copying machine.
In a digital color copying machine, the reflectance of a color image on an original is read by color-separating each pixel into three colors of R (red), G (green) and B (blue), and the read result is converted to RGB three-color digital image data. The three-color digital image data is subjected to color correction processing, such as density conversion processing, filtering processing, black signal generation processing and tone processing, thereby producing four-color digital image density data of C (cyan), M (magenta), Y (yellow) and K (black).
Based on the four-color digital image density data, a dot image, which is a digital image, is recorded on copying paper.
In a conventional digital copying machine or printer, when a black character is to be recorded, one black color material is used. The reason is that if plural color materials are used to record a black character, chromatic blur will occur around the black character due to displacement among the color materials, and such chromatic blur needs to be prevented.
However, in a method of recording a black character by uniformly using one black color material, when a black character is to be recorded on a colored background, a white portion will occur around the character due to displacement of color materials and this will degrade the image quality. The higher the density of the background, the greater the degradation in image quality.